| 1. |
- Purwandari, F. A., et al.
(author)
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Pretreatment of oil palm empty fruit bunch (OPEFB) by N-methylmorpholine-N-oxide (NMMO) for biogas production: Structural changes and digestion improvement
- 2013
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 128, s. 461-466
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Journal article (peer-reviewed)abstract
- Pretreatment of OPEFB (oil palm empty fruit bunch) by NMMO (N-methylmorpholine-N-oxide) on its subsequent digestions was investigated. The pretreatments were carried out at 90 and 120 degrees C for 1, 3, and 5 h in three different modes of dissolution (by 85% NMMO solution), ballooning (79% NMMO solution), and swelling (73% NMMO solution). The total solid recovery after the pretreatment was 89-94%. The pretreatment process did not have a major impact on the composition of OPEFB, other than a reduction of ash from 5.4% up to 1.3%. The best improvement in biogas production was achieved by a dissolution mode pretreatment of OPEFB, using conditions of 85% NMMO, 3 h, and 120 degrees C. It resulted in 0.408 Nm(3)/kg VS methane yield and 0.032 Nm(3) CH4/kg VS/day initial methane production rate, which correspond in improving by 48% and 167% compared to the untreated OPEFB, respectively.
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| 2. |
- Wikandari, Rachma, et al.
(author)
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Fermentation inhibitors in ethanol and biogas processes and strategies to counteract their effects
- 2019
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Book (other academic/artistic)abstract
- Bioethanol and biogas production are the most common fermentation process to convert organic waste into energy. The presence of inhibitory compounds affects the performance of fermentation, leading to lower product yield. The inhibitory compounds for bioethanol and biogas might be different due to the different types of microorganism used for the process, in which bioethanol process uses a single culture, while biogas process uses a mix culture of microorganisms. However, in general, the inhibitors can be classified into three groups. The first group is natural inhibitor exist in the raw material such as flavor compounds or chemical compounds that contaminates available in the waste stream such as heavy metals, light metals, antibiotics, and pesticides. The second group is inhibitor that forms during the fermentation process such as ammonia, sulfide, and ethanol. The third group is inhibitor which is formed during the pretreatment of lignocellulose such as furfural, hydroxymethylfurfural, phenolic compounds, and humic acid. The minimum inhibitory concentration and inhibition mechanism will be discussed in this chapter. The inhibition effects can be reduced or removed by choosing a suitable concentration of the substrates and choosing a proper method for the pretreatment and/or hydrolysis steps. When the toxic compounds are available in the substrate, detoxification could be an option, although it has some expenses and might lead to partial loss of sugars. However, choosing a right strategy for the fermentation by selecting a suitable process, for example, fed-batch or continuous mode with high cell density or encapsulated cells, using a tolerant organism or an organism that can convert the inhibitors, might avoid the necessity of detoxification.
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